1. Field of the Invention
This invention is related in general to autonomous vehicles and other equipment operating in a surface facility and, in particular, to a method for establishing a potential zone of operational presence for each autonomous component in the system to ensure safety and efficiency.
2. Description of the Related Art
Traffic of manned or autonomous vehicles in a system is normally controlled by tracking the position of each moving component in the system and by communicating with each vehicle, either from a central location, from a peripheral position, or directly from other vehicles, to guide the vehicle safely along a desirable course. The worldwide air-traffic control system is a good example of such an approach. The position of each airplane is continuously monitored by one of many air-traffic control centers that is also in constant communication with the airplane in order to alert its crew of any impending danger or other situation deserving of attention. When the aircraft is unmanned, the communication includes control signals to an on-board computer that controls the flight of the craft through appropriate software and electronic and mechanical hardware. That is how an unmanned spacecraft is guided in flight. Thus, for the purposes of this disclosure, the term xe2x80x9cautonomousxe2x80x9d is intended to refer to the availability of either on-board or off-board supervisory systems for controlling the movement of a vehicle.
Autonomous vehicles in a surface mine operation can be similarly monitored and controlled by a central or satellite center transmitting control signals to the vehicle""s on-board computer based on current mine conditions and in response to position data communicated by the vehicle. Alternatively, the vehicles""s own on-board computer can produce appropriate control signals to the vehicle as a function of its position and additional information received from external components of the guidance system. Knowing the current position of the vehicle with respect to known fixed obstacles and other mine equipment, the vehicle can be maneuvered to destination by the continuous control of its operating functions (for example, steering-wheel, accelerator and brake position of a truck). An on-board satellite-based positioning system (such as GPS) or an equivalent positioning unit (either of which can be supplemented with an inertial navigation system or the like) can be used to determine the current position of the vehicle, with an on-board transmitter/receiver unit to communicate with the control center, and on-board microprocessing and storage modules with appropriate hardware and software can also be used to effect the actual movement of the vehicle. Every operating function is manipulated to cause the vehicle to follow a predetermined trajectory or a set of alternative trajectories that can be modified by current control instructions to meet particular up-to-date traffic conditions. Hazards are avoided by implementing a predetermined control response when a hazard is identified by the system. For example, if a potential obstacle is detected within a certain distance of the vehicle being monitored, the path of the vehicle is modified to avoid collision.
This traffic control approach is effective for systems operating at near steady state most of the time, such as in the case of airplanes that follow predetermined flight paths from a starting point to destination. When rapidly changing conditions exist, though, such as within the traffic of a surface mine where multiple vehicles and other equipment cross paths and change direction and speed as required to perform multifaceted functions and to meet continuously changing optimal mine-operation alternatives, a rigid, strictly reactive system of accident prevention is not adequate. A larger degree of flexibility is required to distinguish between different kinds of hazards. For example, while an unidentified obstacle approaching a vehicle traveling at 30 miles per hour along a predetermined path on a mine road may warrant the immediate stoppage of the vehicle, the approaching of a known potential obstacle, such as another vehicle traveling in the opposite direction, may only require a reduction in speed and an additional precautionary adjustment, such as a shift to the appropriate side of the roadway. Accordingly, a more flexible, dynamic approach is required. This invention is a component of such a new approach to mine traffic and safety control, an approach that provides a dynamic response through the implementation of various novel control concepts.
Surface mines utilize a variety of work machines for excavating and transporting ore, grading and stabilizing roadways and slopes in the mine pit, and for providing all support functions necessary for the operation of a mine. Most work and haulage machines have been human-operated, mobile pieces of equipment constantly being moved around the surface of the mine. Skilled operators ensure that each machine or vehicle is positioned in the right place and optimally oriented to perform its intended function while avoiding accidents and injury to people and property. In order to improve efficiency, much effort is currently under way to develop automated systems for controlling the operation of such work machines in surface mines and other environments. Therefore, this invention is described in the context of a surface mine operation, but its concept is applicable to any operation involving moving equipment (such as at waste sites and in underground mining, or in digging, shipping, trucking, and automotive operations) and should not be understood to be limited to surface mines.
The primary objective of this invention is a safety monitoring and control system for ensuring the avoidance of hazards by all moving vehicles and equipment operating in a surface mine.
Another objective is an approach that permits the dynamic adaptation of a set of safety control rules to current circumstances facing a moving vehicle in a mine.
Another goal of the invention is a system that detects potential collision hazards in the path of an autonomous vehicle and effects an emergency stop when the vehicle travels in an otherwise unavoidable collision course.
Still another objective is a hazard avoidance system that utilizes apparatus suitable for implementation as a removable module for each autonomous vehicle in a multi-vehicle operation, particularly a surface mine.
Another goal is a system that is suitable for automated implementation with current surface-mine haulage and mining equipment.
A final objective is a system that can be implemented economically according to the above stated criteria. Therefore, according to these and other objectives, the preferred embodiment of the present invention consists of linking each autonomous vehicle and/or other moving equipment in a surface-mine facility to a control center for communicating data and control signals. The function of each autonomous vehicle is performed by causing it to track a predetermined trajectory related to its particular task and is implemented with on-board GPS and two-way communication hardware. In addition, the current position of the vehicle is continuously monitored and correlated to the position of potential hazards along its path, so that corrective action can be taken by implementing appropriate, predetermined control strategies.
According to one aspect of the invention, each vehicle is assigned a safety zone of operational occupancy (defined as a xe2x80x9csafety envelopexe2x80x9d) that allows for the vehicle""s actual physical presence and operating tolerances. The safety envelope is characteristic of each vehicle and is defined by a variable volume surrounding the vehicle wherein it may be physically present as it travels along its intended trajectory. According to another aspect of the invention, the shape and size of the safety envelope is dynamically varied to meet safety requirements for current trajectory conditions facing the vehicle as it performs its autonomous function along its predetermined path. The safety envelope is changed according to a predetermined set of rules specific to the vehicle. Thus, this zone of potential presence represents a volume of assumed occupancy under given conditions and is dynamically adjusted for each vehicle as circumstances change during the performance of its autonomous function.
According to yet another aspect of the invention, intersections and switch locations among the various predetermined paths and roadways available within the mine""s property are identified dynamically by monitoring current traffic conditions and establishing locations where the safety envelopes of vehicles traveling along approaching trajectories could overlap. If an overlap of safety envelopes is possible, the trajectories are treated as merging or crossing, depending on their configuration, and the vehicles are controlled by a corresponding set of rules applicable to switches or intersections, as applicable. If an overlap is not possible even under worst-case conditions, the vehicles are not subjected to this additional layer of safety control.
Various other purposes and advantages of the invention will become clear from its description in the specification that follows and from the novel features particularly pointed out in the appended claims. Therefore, to the accomplishment of the objectives described above, this invention consists of the features hereinafter illustrated in the drawings, fully described in the detailed description of the preferred embodiment and particularly pointed out in the claims. However, such drawings and description disclose but one of the various ways in which the invention may be practiced.